1. Field of Invention
This invention relates to a clamping system incorporating flexible clamps or clips for securing photovoltaic modules, panels, and plates against support structures and frames.
2. Prior Art
Generally solar photo voltaic (PV) modules are attached to support frames mounted on rooftops, poles, and other surfaces with various means of clamping techniques. These clamping methods must provide sufficient force to insure that the modules will remain in place against their associated support frames even under very high wind loads. Examples of prior art are shown in FIGS. 1-4.
Typical clamping methods utilize various forms of edge holding clamps that clamp on top of the panel and hold the panel against a base or structural member using a bolt or screw for attachment. The structural member is typically a rail style member such as a commercial strut channel. FIG. 1 illustrates typical clamps for clamping solar panels to strut bases.
Currently there are many forms of clamps that are used for panel or plate clamping applications. For clamping two panels adjacent to each other with a common clamp there are two popular configurations: the T-clamp (FIG. 2) or flanged U-clamp that grips two adjacent panel edges and clamps them to a common strut channel. U.S. Pat. No. 6,672,018 describes the T-clamp and its clamping method. Typically the clamp is made shorter than the height of the panels in order to insure proper clamping action. The major problem with this type of apparatus is that since it is shorter than the panel that it is clamping, it will not stay in place and will fall off of the edge if only one panel is present. The second adjacent panel must be put in position first so that the T-clamp or U-clamp can be supported by both panel edges. Unfortunately this limits its usefulness since panels are typically installed in sequence. And since they are typically installed on an inclined surface such as a roof, it is difficult for a single installer to temporarily hold the first panel in position and simultaneously bring the second panel into position for clamping.
T-clamps and U-clamps can be made longer than the part that they must clamp, however they still will not clamp the first panel in place without large forces needed to overcome their stiffness. These clamps are therefore also difficult to use for this application.
Currently there are other types of clamps that are used for clamping a single panel edge into place. One of the most popular types of clamps for this application is the Z-clamp (FIG. 3). The Z-clamp grips the top of the module with its upper lip and clamps to the strut channel using a bolt through the lower lip of the clamp. It is typically made intentionally short to insure gripping. Unfortunately this method of clamping with an intentionally short clamp has a tendency to pivot or slip away from the panel module edge causing loss of clamping force and consequent panel disengagement. Also, since the panel height varies, the height of the clamp must also vary in order to meet the appropriate height requirement. This leads to the need for a number of different height clamps because they have no adjustability. It is also difficult to uniformly clamp the panel into place because of the need for intentionally shorter Z-clamps.
An L-clamp (FIG. 4) forming an inverted L shape when clamped against the panel can also be used for clamping the panels in place. However, unless it is made exactly the correct height it will create an uneven force on the panels causing stress concentrations and slippage toward or away from the panels.
Although there are many conventional clamps for clamping PV modules and panels to structures they all suffer from the following disadvantages:
Existing T-clamps and U-clamps that are shorter than the panel height tend to slip or fall off of the initial panel if not held in place before the adjacent panel can be positioned next to it. This increases the assembly labor because the clamp must be temporarily held in place until the next panel is positioned next to it.
Existing T-clamps and U-clamps that are longer than the panels also suffer from their limited usefulness in clamping the first panel.
Because of the solar panel thickness tolerances, existing Z-clamps and other end clamps are constructed intentionally shorter to insure proper gripping. However bolting down the base causes the top edge to slip away from the panel edge while tightening (See FIG. 3).
Existing end clamps do not squarely clamp the panel edge and can create stress concentrations on the outer panel edges when tightened.
In summary there is a need for flexible height clamps that can provide sufficient clamping force without causing slippage or stress concentrations on the devices being clamped.
3. Objects and Advantages
The present invention is a flexible clamp that is formed to provide the flexibility needed to clamp variable height panels or flat surfaces. The clamp is tightened against the panel with a bolt through the clamp. The clamp configuration for the required deflection path is in the form of an arch or C, rectangle, or other folded shape. An important feature of the clamp shape is the ability to apply asymmetric deflection and consequent forces against the components to be clamped.
There are a number of objects and advantages of this invention over existing clamping systems.
The tolerance in the height of the solar panel is no longer critical for proper clamping because the clamp's inherent flexibility allows height variations.
Unlike most solar clamps the pivot point for tightening is located above and outside the clamp tightening bolt. This means that as bolt tightening proceeds the clamp rotates towards the panel instead of away from it insuring positive contact.
When clamping two panels with this clamp the first panel can be secured by initial tightening and it still allows the second panel to be inserted under the clamp flange to be tightened.
Because of its flexibility the clamp's bearing surface adjusts angularly to the panel surface angle and provides more uniform loading—compared with Z-clamps that provide little or no flexibility and instead create corner stress concentrations.
The flexible configuration of the clamp allows it to act as a stiff hinge and provide a relatively constant force to the panel even when temperature changes or stresses cause slight thickness changes in the solar panel.
The flexible clamp when formed into an undulating profile allows it to be used in tight spaces and still retain its flexibility.
The flexible clamp properties allow it to withstand the dynamic loads and vibrations associated with solar panels subject to high wind loads and solar tracking.
Further objects and advantages will become apparent from a consideration of the drawings and ensuing description.